xfs: fix uninitialized list head in struct xfs_refcount_recovery

xfs: fix uninitialized list head in struct xfs_refcount_recovery

Source kernel commit: c1ccf967bf962b998f0c096e06a658ece27d10a0

We're supposed to initialize the list head of an object before adding it
to another list.  Fix that, and stop using the kmem_{alloc,free} calls
from the Irix days.

Fixes: 174edb0e46e5 ("xfs: store in-progress CoW allocations in the refcount btree")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Carlos Maiolino <cem@kernel.org>